How to create reports for C code with clang

Following the directions on the main page of the static clan analyzer ( http://clang-analyzer.llvm.org/scan-build.html ) ...

I have a small C file that is badly fixed ( badcode.c):

int main(int argc, char ** argv)
{
    int j;
    int a[4];
    puts(a[j]);
    return 'a';
}

To get a basic idea of ​​how the words of the static clang analyzer (scan-build) are executed, follow these steps:

scan-build -v clang badcode.c

It outputs:

scan-build: Emitting reports for this run to '/tmp/scan-build-2012-08-17-1'.
scan-build: 'clang' executable not found in '/usr/share/clang/scan-build/bin'.
scan-build: Using 'clang' from path: /usr/bin/clang
badcode.c:7:2: warning: implicit declaration of function 'puts' is invalid in C99 [-Wimplicit-function-declaration]
        puts(a[j]);
        ^
1 warning generated.
scan-build: Removing directory '/tmp/scan-build-2012-08-17-1' because it contains no reports.

Ok, great, clang gives a little warning, but a.out is still being generated. And why is this not reporting? A unified variable jshould be a painfully obvious red flag for any static analyzer - why is this not being reported?

Am I just using the wrong command line arguments?